Benjamin Braddock is arriving back in Los Angeles by plane. He has just graduated from college and has his entire life ahead of him. He is smart, his family is wealthy and he’s got connections to help with his degree when it comes to the transition into the world of work. Nevertheless, Benjamin is unhappy. More than unhappy, he is overwhelmed by a sense of ennui.
Back at home, his family is throwing him a welcome home party. Ben remains detached and expressionless, seeming emptied of all emotion. Congrats are tossed his way for graduating and the almost entirely older guests are quick to give advice. Outside by the pool, one of his father’s friends sums up every bit of his advice on how Ben can get ahead in the world with one single word: plastics. Overcome with a sense of the world closing in on and no escape hatch, Ben tries to get away in the only way possible; he runs inside and hides behind the oversized aquarium.
The door opens and his family’s older friend Mrs. Robinson seems to have mistaken the room for the bathroom. Benjamin directs her to the bathroom, but Mrs. Robinson remain, smoking a cigarette and probing for the cause behind why he is so obviously bothered by something. She suddenly asks if he would mind driving her home.
When they get to her house, Benjamin reluctantly accepts her invitation to come in. She pours drinks, puts on music and engages in awkwardly honest conversation. Benjamin takes note that the evening is taking a strange turn and then realizes that Mrs. Robinson has been attempting to seduce him.
She asks him if he’s ever seen the portrait of her daughter Elaine and then takes him into her daughter’s bedroom to show him the painting. For the first time since stepping off the plane, Benjamin seems impressed and almost happy as he admires the portrait. Meanwhile, Mrs. Robinson starts to undress and asks Ben for help with the zipper. Feeling uncomfortable again, he tries to avoid her, but she once again assures him that she is not trying to seduce him.
He decided to leave, but before he can get out of the house, Mrs. Robinson calls out for him to retriever her purse before he goes. Mrs. Robinson is waiting for him in the bathroom, naked. Overcome with anxiety, Ben merely wants to leave, so Mrs. Robinson tells him that any time he wants her, he can have her. The sound of a car outside sends him running past her and he runs into Mr. Robinson downstairs and nervously attempts to explain what he’s doing there.
Mr. Robinson calms his down, mixes and drink and the two discuss Ben’s plans for his future. Then he offers some fatherly advice in the form of telling Ben to lighten up and fool around a little before finding one girl to settle with. As he leaves, Robinson reminds him that Elaine is coming back from college soon, too.
Another party. Benjamin is turning 21 and his parents prepare their guests for the big reveal, it is revealed that Benjamin is wearing a scuba diving outfit. He goes to the pool and sinks to the bottom, lying there motionless.
The next image of Benjamin is inside a phone booth at the Taft Hotel from where he’s called Mrs. Robinson to inform he didn’t get a room. She says she will only be an hour. When Mrs. Robinson arrives, he goes to the front desk and gets a hotel room under the name Gladstone. The atmosphere inside the hotel room is one of utter awkwardness for Benjamin. She finally taunts him into action by slyly telling him that being a virgin is nothing to be ashamed of.
Ben’s life for the next few weeks is one that swings back and forth between bored loafing at home and sleeping with Mrs. Robinson in hotel rooms. Neither seems to bring Benjamin particularly great pleasure and one day his father is moved to ask exactly what he is doing. Ben replies that he is drifting. His father responds that a time comes in everybody’s life when they need to take stock and get off their butt.
The next time he’s with Mrs. Robinson in the hotel, he asks if they could just once talk to each other; all they ever do is have sex. The conversation proceeds to reveal that she and Mr. Robinson are no longer intimate and she only married him because she got pregnant with Elaine. This is a revelation she admonishes him to never tell her daughter. After finding out she gave up her pursuit of a career in art, he suggest that maybe might ask Elaine out on a date to which she vehemently expresses opposition. Ben takes this as evidence she doesn’t think he’s good enough for her daughter and gets angry himself. She defuses the situation by telling him that she would never say he’s not as good as person as Elaine and this keeps him from leaving and gets him back into bed.
His parents begin to press him about asking Elaine out and he struggles to avoid the situation, but is soon showing up to a stone-faced Mrs. Robinson waiting for her daughter to get ready for her date with Benjamin. Ben tries to tell he was pressured into it by his parents, but she remains cold and aloof and bitter.
The date does not go well. Benjamin is just trying to rush through the evening and generally behaves like a giant jerk to Elaine, who tries to remain and sweet and pleasant as possible. Even when the date turns out to include a visit to strip club. When she starts crying and runs from the club, Benjamin tries to explain that he was pressured by his parents and that he’s really not at all like this guy he was pretending to be. He kisses her and by the time they are eating inside his car at a drive-in restaurant, he is spilling his guts about how everybody around him makes him feel as though he is playing some sort of bizarre game where he hasn’t been given the rules.
They wind up at the Taft Hotel where he tries to explain why the entire staff seems to mistake him for some Mr. Gladstone person. When they leave the hotel and are back parked in the car, he confesses that she is the first person he can stand to be with for so long he can barely remember. After a pause, she directly asks if he is involved in an affair to which he admits that it was something that just happened. When asked if the woman is married, he prevaricates by answering she’s married and has a son.
When Benjamin shows up for a second date the day, Mrs. Robinson confronts in the parking lot, ordering him to park farther down the block. She then proceeds to order him to never see her daughter again, threatening him with the promise to tell Elaine all about her affair with him. He responds by running toward the house and calling for Elaine. He even goes up to her room and begins to launch into the true story about the married woman. Mrs. Robinson appears behind Elaine and Ben freezes. The situation slowly becomes clear to Elaine and she yells at him to get out.
Over an unexplained period of time, all Benjamin seems to do is try to get a glimpse of Elaine. One day he announces to his parents that he is going to marry Elaine Robinson despite the fact that she doesn’t like him. Despite this obstruction, Ben heads to Berkeley where Elaine is attending college. He spots her walking with a guy. He takes up rent at a rooming house. He continues spying on Elaine. He follows her bus ride to the zoo and tags along behind her until she finally demands to know what he’s doing. Ben meets Elaine’s boyfriend, Carl.
A few days later, Elaine shows up at Ben’s rooming house, demanding to know he could possibly rape her mother. Elaine then proceeds to give her mother’s version of the story which differs considerably from what has been portrayed on screen. Benjamin then tells her what really happened and she leaves. Coming back later that night, Benjamin asks her to marry him, but she gives him a non-committal answer. The next day, however, they discuss the blood test required for a marriage license. For the next few days, Benjamin relentlessly pursues her, even after she tells that Carl has also proposed.
Later on, he buys an engagement, but when he returns to his room, Mr. Robinson is there waiting for him demanding a full accounting. He then informs Ben he is divorcing his wife and when Benjamin says he doesn’t lover her, but his daughter, the man attacks him, promising him a life behind bars if he pursues Elaine.
When he tries to see Elaine again, he only receives a note informing him she loves him, but they would never work out together. Ben determinedly goes to the Robinson house, climbs the fence and sneaks inside, climbing his way up to Elaine’s room where Mrs. Robinson is packing. She calls the police and he makes a break for it. He drives back to Elaine’s school and at Carl’s frat house finds out the two of are getting married in Santa Barbara.
Benjamin makes a desperate to drive to Santa Barbara before the wedding can take place. He discovers the location of the ceremony and as he gets closer, his car runs out of gas. He jumps out and takes off on foot. At last, he makes it to the church and runs up to the balcony which is located behind a pane of glass. The ceremony is already underway and drawing to a close so he starts yelling and pounding on the glass. Mr. Robinson starts toward him, but Mrs. Robinson pulls him back telling him that he’s too late.
Confusion has interrupted the nuptials and then suddenly Elaine turns toward the balcony and loudly yells Ben’s name. Ben runs as fast as he can down toward the ceremony and after Mrs. Robinson slaps her daughter twice, Elaine breaks free and runs out of the church with Benjamin who has grabbed a cross off the wall and uses as a wedge to keep the doors from being opened so they can be followed.
The two of them run off toward where a city bus is approaching and Ben flags the vehicle to a stop. They both step inside and take the bench seat across the back. After laughter and celebration of their success, they both stare off into the faces of all those on the bus who have turned their heads to look at them.